However three male inmates tested positive for drugs and their reported confession of trading 20 cigarette packs for one yaba tablet from a fellow inmate prompted officials to investigate further.
Provincial Police Region 3 deputy chief Pol Maj-General Chakthip Lohasudsakul and prison director Sudsawad Sancharoen led the 500-strong team to search the prison cells for drugs and other contraband at 4am, according to police.
They found home-made spikes along with cigarettes and cartoon books with porn pictures hidden inside.
The officials focused on Zone 1 inmates and also conducted urine tests.
A ball of plasticine containing 190 yaba tablets was thrown over Sakhon Nakhon Prison’s 5.8-metre-high wall, but patrol guards intercepted it before inmates were released into the yard yesterday morning.